netdev - [PATCH net 2/2] socket: don't clear SOCK_TSTAMP_NEW when SO

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Date:   Fri, 9 Oct 2020 12:31:21 +0200
From:   Christian Eggers <ceggers@...i.de>
To:     "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Deepa Dinamani <deepa.kernel@...il.com>
CC:     Willem de Bruijn <willemb@...gle.com>,
        Christoph Hellwig <hch@....de>, <netdev@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, Christian Eggers <ceggers@...i.de>
Subject: [PATCH net 2/2] socket: don't clear SOCK_TSTAMP_NEW when SO_TIMESTAMPNS is disabled

SOCK_TSTAMP_NEW (timespec64 instead of timespec) is also used for
hardware time stamps (configured via SO_TIMESTAMPING_NEW).

User space (ptp4l) first configures hardware time stamping via
SO_TIMESTAMPING_NEW which sets SOCK_TSTAMP_NEW. In the next step, ptp4l
disables SO_TIMESTAMPNS(_NEW) (software time stamps), but this must not
switch hardware time stamps back to "32 bit mode".

This problem happens on 32 bit platforms were the libc has already
switched to struct timespec64 (from SO_TIMExxx_OLD to SO_TIMExxx_NEW
socket options). ptp4l complains with "missing timestamp on transmitted
peer delay request" because the wrong format is received (and
discarded).

Fixes: 887feae36aee ("socket: Add SO_TIMESTAMP[NS]_NEW")
Fixes: 783da70e8396 ("net: add sock_enable_timestamps")
Signed-off-by: Christian Eggers <ceggers@...i.de>
---
 net/core/sock.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/net/core/sock.c b/net/core/sock.c
index 3926804702c1..f09053dfb12c 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -757,7 +757,6 @@ static void __sock_set_timestamps(struct sock *sk, bool val, bool new, bool ns)
 	} else {
 		sock_reset_flag(sk, SOCK_RCVTSTAMP);
 		sock_reset_flag(sk, SOCK_RCVTSTAMPNS);
-		sock_reset_flag(sk, SOCK_TSTAMP_NEW);
 	}
 }

-- 
Christian Eggers
Embedded software developer

Arnold & Richter Cine Technik GmbH & Co. Betriebs KG
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